GENETICS

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GENETICS

• THE SCIENCE OF HEREDITY

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HEREDITY AND MENDEL GENETICS
1. TRAIT
2. HEREDITY
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3 4. GENE and LOCUS
homologous
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5. ALLELES
The different forms of a gene for a particular
trait. Example A , a
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6. DOMINANT ALLELE
The form of a gene that is expressed and prevents
the expression of the other form. They are shown
with capital letters like A, B, C etc.
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7.RECESSIVE ALLELE
The form of a gene that is expressed only when
paired with a gene coding for the same trait.
They are shown with lowercase letters like ,a, b,
c etc.
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8.HOMOZYGOUS (PURE BREED)
When both alleles are same. Example BB , bb
9.HETEROZYGOUS (HYBRID)
When the alleles are different. Example Bb
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10. PHENOTYPE
Example Tall pea plant
11. GENOTYPE
Examples Heterozygous tall pea plant or
Homozygous tall pea plant
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12. PARENTAL GENERATION(P)
Example tall stem X dwarf stem
13. FIRST FILIAL GENERATION (F1)
14. SECOND FILIAL GENERATION (F2)
(selfing of the F1 generation)
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15. MONOHYBRID CROSS
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16. DIHYBRID CROSS
Ex round, yellow seeded X wrinkled, green seeded
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17.TEST CROSS
Test cross is used to determine if an individual
exhibiting a dominant trait is homozygous or
heterozygous. Example Phenotype tall
X dwarf Genotype T?
tt (TT or Tt) 1. 100tall
2. 50 tall 50 dwarf
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18. PUNNET SQUARE
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19. PEDIGREE CHART
Example ALBINIZM
i
ii
IDENTICAL TWINS
iii
FRATERNAL TWINS
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19. PROBABILITY

• The Rule of Independent Events Previous events
  do not affect the probability of later
  occurrences of the same event.
• Ex. Probability of having a head or tail in a
  toss is ½

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B. The Product Rule The probability of
independent events occurring together is equal to
the product of the probabilities of these events
occurring separately. Ex. Probability of having
one head and one tail is ½ x
½ ¼
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What are the chances that a baby will be born a
male or female?
Each baby has a 5050 chance of being either a
male or a female. It doesn't matter how many
other brothers or sisters are already in the
family. Each baby is a separate entity and its
sex is not influenced by the sexes of earlier
children.
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• Olasilik ve Genetik
• Prensip Sansa bagli bir olayin bir defa
  denemesinden elde edilen sonuçlar, ayni olayin
  daha sonraki deneme sonuçlarini etkilemez.
• 10 defa attigimiz paranin 10 defa da tura
  gelmesi halinde 11. defa tura gelme sansi yine
  1/2 dir.
• Genotipi Aa olan bir bireyin gametleri 1/2 A ve
  1/2 adir.

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• Olasilik ve Genetik
• 2. Prensip Iki bagimsiz olayin birlikte olma
  sansi onlarin ayri ayri olma sanslarinin
  çarpimina esittir.
• Iki tavla zarini birlikte attigimizda bunlardan
  birinin 4 gelme sansi 1/6 dir. Diger zar içinde
  aynidir.Ayni anda 4 gelme olasiligi 1/36 dir.
• Bir ailenin dogacak 3 çocugundan ikisinin
  erkek birinin kiz olma olasiligi (a kiz, b
  erkek)
• (ab)3 a 3 3 a2 b 3 b2 a b3
• 3b2 a 3 (1/2) 2 ( 1/2) 3/8

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• How meiosis produces genetic variation???
• 1. Without meiosis, chromosome numbers would
  continually increase
• 2. Meiosis ensures daughter cells receive one of
  each kind of gene precisely halves the
  chromosome number
• 3. Independent assortment provides 2n possible
  combinations of chromosomes in daughter cells
• 4. In humans with 23 haploid chromosomes, 2n
  223 8,388,608 possible combinations.
• 5. Variation is added by crossing-over if only
  one crossover occurs within each bivalent, 423 or
  70,368,744,000,000 combinations are possible
• 6. Fertilization also contributes to genetic
  variation (223)2 70,368,744,000,000 possible
  combinations without crossing-over
• 7. With fertilization and crossing-over, (423)2
  4,951,760,200,000,000,000,000,000,000
  combinations are possible